In recent years, anion exchange membrane fuel cells (AEMFCs) have drawn more attention by showing high performance and potentially allowing catalysts based on more abundant materials. One frequently overlooked parameter in these systems is membranes permeability, often referred to as gas crossover. This undesirable phenomenon creates mixed potentials and also hotspots with temperatures high enough to cause membrane defects and pinholes. Therefore, it is important to investigate it quantitatively at conditions where a fuel cell often operates. In this study, hydrogen and oxygen crossover of several Aemion anion exchange membranes (AEMs) are measured with mass spectrometer (MS) at various relative humidities (RHs) and temperatures. The proton exchange membrane (PEM) Nafion is also investigated for a comparison. AEMs are generally less permeable to oxygen and hydrogen than PEM. The first-generation AEMs show a decreasing trend in permeability with RH, opposite to PEM. The second-generationAEMs are much less affected by RH levels. The measured oxygen crossover was two to six times lower compared to hydrogen crossover, depending on the membrane type and RH. The influence of membrane interface on crossover is evaluated to be higher for reinforced membranes, but overall smaller compared to the bulk contribution. Overall, AEMs show lower crossover than PEM, and from that perspective making them more suitable and a safer choice for fuel cell and electrolysis applications.